RFC: On-demand package installation API in kdelibs

[Lubos Lunak]

 Hello,

 I'd like to add API somewhere to kdelibs that would make it easy for 
applications to install additional packages if they find out some 
functionality is missing. The 11.3 release of openSUSE already has this 
feature, you can read about it at [1].

 In short, there are actually quite some places in KDE where this could be 
used, but currently the code just does some kind of error message and shrugs 
it off:
- Nepomuk will give a notification about Virtuoso not being available and 
that's it
- Amarok will complain about MP3 support not being present (which is the case 
by default with some distributions because of legal reasons) and will try 
running a specific script to install it
- DrKonqi has another implementation of running an executable for installing 
debug packages, specified as CMake argument
- clicking on some files in e.g. Dolphin can show the 'Open with...' dialog if 
no application has been found to handle the file, but then usually the dialog 
is useless if the application is not installed
- and so on

 In most of these cases the user has to manually do what can be done 
automatically with today's packaging systems, and in fact those can do it 
better, since they can much more easily find out which package can handle 
mimetype application/foo or provide binary bar.

 So the idea is to provide simple API in the form of 'bool 
tryToEnsureInstalled{MimeType|Binary|Whatever}( QString name )'. Various KDE 
code will call it when it finds out something is missing and maybe the call 
solves the problem.

 I'm currently not proposing any specific code, as I'm first interested in 
feedback. The openSUSE 11.3 kdelibs code is in [2] (that's including making 
KRun use it before resorting to KOpenWithDialog), an example of use can be 
e.g. the patch at [3] making Amarok use this API instead of its own code.

 The idea is that upstream kdelibs only provides a header file (attached is 
the public API as used in openSUSE) and dummy code, packages would/could 
provide their implementation that'd actually do the work. KDE developers 
would just basically change from
'if( !somethingNeeded()) { complain(); return false; }'
to
'if( !somethingNeeded() && !KSUSEInstall::install( "somethingNeeded" )) 
{complain(); return false; }'.

 I'm not sure what to call it (KInstall?) and where to put it - this is needed 
by KRun in libkio and may be even later needed by something lower, but it 
should be able to use kdeui).


 Comment, questions, suggestions?


[1] http://www.kdedevelopers.org/node/4232
[2] 
https://build.opensuse.org/package/view_file?file=ksuseinstall.diff&package=kdelibs4&project=KDE%3ADistro%3AStable
[3] 
https://build.opensuse.org/package/view_file?file=ksuseinstall.diff&package=amarok&project=KDE%3ADistro%3AStable

-- 
 Lubos Lunak
 openSUSE Boosters team, KDE developer
 l.lunak at suse.cz , l.lunak at kde.org
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